Your thoughts on a buffer sharing mechanism for FreeBSD (dma-buf for drm2)

Bas Vermin bas_vermin at
Tue Dec 25 23:38:18 UTC 2012

Hi Guys,

Today I decided to do something useful for the FreeBSD community, working on the TTM and KMS for the AMD graphics cards which I think a lot of people could use.

As most of us know Intel KMS support was added to FreeBSD a few months ago, and as far as I know this code was based on the Linux 3.1 kernel. The FAQ in the wiki states that in order to keep this code up to date the Linux commit log would be checked and changes merged into FreeBSD. Then came Linux 3.3 which added support for dma-buf, the buffer sharing mechanism to be used by PRIME for offloading work to different GPU's, a feature we obviously want. The problem with dma-buf is that it is licensed under the GPL and has now littered all over the otherwise MIT licensed drm code (even nVidia wasn't allowed to use dma-buf for their propietary driver).

My question is, does such a buffer sharing mechanism exist in FreeBSD?
And if so, would it be somewhat compatible with what dma-buf is doing in the PRIME code?

If not I think such a mechanism should be created, prehaps part of the vm system (not separate as dma-buf is). Or am I just being stupid and is there a much better way of solving this problem?

I'd like your thoughts on this.


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